This invention relates generally to the field of fiber optic signal transmission coupling devices used to interconnect a pair of terminated optical fibers for light transmission therethrough, and more particularly to an improved device of this type incorporating means for varying the gap between the ends of the aligned terminated optical fibers in a controlled manner to provide variable optical attenuation to a transmitted signal. Devices of this general type are known in the art, and the invention lies in specific constructional details permitting improved ease in adjustment, as well as simplification of the manufacture of the component parts and the assembly thereof.
In the prior art, there exist a variety of structures for introducing variable attenuation. Some structures include a wheel having a plurality of neutral density filters which are selectively introduced into the gap. Others employ a movably mounted reflective surface. Still other methods employ heating and twisting of the fibers.
The U.S. Pat. No. 4,145,110 granted Mar. 20, 1979 to Otti Szentesi, discloses a relatively low-cost device to accomplish this purpose in which a connecting structure firmly holds one terminated fiber in relatively fixed position, while varying the other fiber using a threaded nut toward and away from the fixed fiber to vary the distance therebetween. While not without utility, the construction is rather large in overall size, precluding use of the same in an area where space limitations are critical, and the construction employs parts which are not easily manufactured using mass production techniques, such as die castings.